Table Of ContentMastering React Test-Driven
Development
Build rock-solid, well-tested web apps with React,
Redux and GraphQL
Daniel Irvine
BIRMINGHAM - MUMBAI
Mastering React Test-Driven Development
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First published: April 2019
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ISBN 978-1-78913-341-7
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To Nige, my first mentor, who taught me the importance of slowing down.
– Daniel Irvine
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Contributors
About the author
Daniel Irvine is a software consultant based in London. He is a member of the European
software craft community and works with a variety of languages including C#, Clojure,
JavaScript, and Ruby. He’s a mentor and coach for junior developers and runs TDD and XP
workshops and courses. When he’s not working, he spends time cooking and practicing
yoga. He co-founded and runs the Queer Code London meetup.
This book would not be what it is without the input of my technical reviewer, Raimo
Radczewski, who is also the author of the expect-redux package that is used in this book. I
met Raimo a few years ago through the European software craft community. We bonded at
a SoCraTes conference and found that we shared many of the same driving forces. Through
many conversations, I learned to respect his thoughtfulness, kindness, and, of course, his
deep knowledge of JavaScript and the React ecosystem. So, when I first took on this project,
I immediately asked Raimo to come on board. Thankfully, he said yes. In the following
eight months, he had a difficult job of reading though many drafts of—shall we
say—variable quality. Those who have worked with me know that I can be lazy, careless,
brazen, and inconsistent. Well, Raimo has seen it all and more, so firstly, I must thank him
for continuing with the project in spite of the early drafts. I must also thank him for
teaching me about many of JavaScript’s nuances, of which I simply wasn’t aware. He also
guided me back toward idiomatic React code, because until I wrote this book I had really
been writing JavaScript “out in the wilderness,” with my own style. He brought me back in
from the cold. He suggested some simplifications to my implementations; for example, the
undo/redo reducer in Section 3, which would have been a great deal more complicated
without his critical eye. I blamed my terrible code on burn-out, but actually, Raimo is a
fantastic programmer and I look forward to the next occasion that we get to work together.
My editor, Keagan Carneiro, has been constantly positive and supportive, not once ever
judging me for missing my self-imposed deadlines, which toward the end I missed
consistently. We got through it in the end. Of all the wonderful things he did for me,
perhaps the most powerful was the push to embrace hooks. When I first informed him in
November 2018 that the React team had announced this weird thing called hooks that
looked horrendous and that I couldn’t ever imagine taking off, but that we might have to
consider doing a chapter on, he turned around and suggested that I rewrite the entire text
entirely to use hooks. Bearing in mind we were halfway through at this point, it was a
pretty big ask. Of course, I knew he was right and I trusted his assessment, so I had to go
through the five stages of grief of denial, anger, bargaining, depression, and acceptance in
super-quick time, before getting on with it. (I believe Raimo is still hovering somewhere
around the bargaining stage.) In the end, we were only delayed by a month, so I have to
thank Keagan for ensuring that the book wasn’t out of date before it was even published.
Sachin Sunilkumar, my technical editor, was wonderfully patient with me as I was
reworking code snippets right until the last moment. He went on a journey of discovery
with me as we built and tested against alpha releases of React. That was fun and stressful
in equal amounts!
There are a number of other friends who stepped in at the last moment to review content
when I was rushing with the final draft. Their assistance was invaluable. The text is much
better for their efforts. Charlotte Payne, Dan Pelensky, Isidro López, Makis Otman, Sam
Szreter, Zach Shaw: thank you. I hope you enjoy seeing your suggested improvements in
print.
To the development team at Idean—in particular, Brendan Murphy, Lucy Monie Hall,
and Zach Shaw—thank you for listening to me bang on about “my book” at least once a
week.
I cannot finish without thanking my partner, Phillipe, who has suffered as I embarked on
this project, my first book. Staying on track while still having a day job was a mammoth
effort for me. It really took it out of me. Phillipe put up with me as I was tired, distracted,
creatively drained, emotionally distraught, unavailable, and—toward the end—burned
out, monosyllabic, and not much fun. He supported me through the project from start to
finish. Thank you.
About the reviewer
Raimo Radczewski is an IT consultant from Berlin, Germany. His journey through the
world of software engineering has taught him not just quite a few languages and
paradigms, but also how to build and lead engineering teams. He's an advocate for test-
driven development and maintains testing tools for the React ecosystem. He organizes
SoCraTes Day Berlin and the Global Day Of Coderetreat, two grassroots communities for IT
workers who are curious about software crafting and eXtreme Programming. His current
focus is founding a tech cooperative to support clients in building a professional and
mindful engineering culture. He tweets under @rradczewski.
Thank you, Daniel, for giving me the opportunity to help create this most excellent
introduction to TDD in React. It will surely land on the bookshelves of many of my
clients. Thank you, Andreas and Jan, for being the first people to show me Test-Driven-
Development and for introducing me to the communities that I continue to learn so much
from.
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Table of Contents
Preface 1
Section 1: Section 1: First Principles of TDD
Chapter 1: First Steps with Test-Driven Development 15
Technical requirements 16
Creating a new React project from scratch 16
Installing NPM 17
Creating a new Jest project 18
Commit early and often 19
Bringing in React and Babel 20
Displaying data with your first test 21
Writing a failing test 21
Writing your first expectation 23
Rendering React from a test 26
Make it pass 27
Backtracking on ourselves 30
Refactoring your work 33
Promoting variables 33
Using a beforeEach block 34
Extracting methods 34
Writing great tests 35
Red, green, refactor 35
Streamlining your testing process 36
Rendering lists and detail views 38
Rendering the list of appointments 39
Specifying list items 44
Selecting data to view 46
Initial selection of data 47
Adding events to a functional component 48
Manually testing our changes 52
Adding an entrypoint 53
Putting it all together with Webpack 54
Before you check in... 56
Summary 57
Exercises 57
Further learning 58
Chapter 2: Test-driving Data Input with React 59
Extracting a test helper 60
Adding a form element 61
